Five days before the first of four people in Britain died of a drug overdose, researchers at a Dutch laboratory organised a nationwide alert over the “Superman” pills that are now believed to have killed those who thought they were taking ecstasy.

But although Public Health England knew of the Dutch warning, no alert was issued in the UK before the fatalities. The NHS body has since argued that there was no evidence at the time that the pills had reached the UK.

Scientists at the Trimbos Institute, in Utrecht, who run the country’s Drugs Information and Monitoring System (DIMS), had arranged for a televised alert in the Netherlands on Friday 19 December, the morning after discovering the pills contained a large, lethal dose of a substance called PMMA (paramethoxymethylamphetamine).

The only immediate alert in the UK was made by Fiona Measham, a professor of criminology at Durham University. She received the alarm from a local drugs testing group on the Friday and considered the warning too important to ignore.

Outside her day job, Measham tests drugs at nightclubs and festivals using a portable mass spectrometer which analyses the makeup of drugs and identifies them by comparing them to a database run by a company called TICTAC Communications at St George’s medical school in south London.

That night, Fat Boy Slim was playing at the Warehouse Project in Manchester, and Measham was due on site to test drugs. She contacted one of the owners, who posted the warning on Facebook and tweeted it to the club’s 145,000 followers.

More than 500 people retweeted the alert. “This was a warning that everyone took seriously who received it,” she said. “Sadly, as far as I know, no other organisations in the UK mentioned Superman until after the first death on Christmas Eve.”

Public Health England said its alerts had to be based on good intelligence, and that was lacking in this case.

John Ramsey, the head of TICTAC, agreed: “I’m not sure what else they could have done.”

But other experts who spoke to the Guardian said the deaths could have been prevented if Britain had an effective early-warning system to detect dangerous drugs that reach the market, and alert the public when needed.

“As soon as the PMMA Superman pills were identified, we should have put out a warning. But we don’t have a website or a proper harm-reduction process that could do this. This is a priority to prevent future deaths,” said David Nutt, professor of neuropsychopharmacology at Imperial College London.

Justas Ropas, a 22-year-old factory worker from Lithuania, collapsed and died at his home in Ipswich. More fatalities swiftly followed. On New Year’s Day, another Ipswich resident, Gediminas Kulokas, died on his 24th birthday after apparently taking the same drug. The deaths of two other men on New Year’s Day, 20-year-old John Hocking from Rendlesham in Suffolk and 27-year-old Daniel Bagnall from Telford, have also been linked to the pills. Inquests on the first three were due to open on Friday.

One of the Superman pills believed to have killed four people in the UK. Photograph: Suffolk police

Small, pink and triangular, the tablets had the “S” Superman logo stamped on both sides and had been sold as ecstasy. Chemical tests found them to be fake: the pills contained no MDMA, the main component of the dance drug. Ramsey, who tested the Superman pills recovered by the Suffolk police, confirmed that they matched the Dutch ones, with the “S” on both sides.

In the Netherlands, people can have drugs checked through DIMS before taking them. The Trimbos Institute sends about 120 unidentified pills and powders for chemical analysis each week.

Scientists at Trimbos have been testing drugs for 20 years, but they were still shocked at the Superman find. TV stations ran interviews with the staff in items that led the news, ensuring millions of people were informed.

Daan van der Gouwe, a scientist at Trimbos, received the email alert that first described the lethal pills on 18 December. Next to the pill’s identification number it said, in large letters: PMMA, 173mg. It was the weekend before Christmas and party season was in full swing.

“We were worried,” he said. “The only thing we could do was issue this warning before everyone was off work.”

Deaths from PMMA are not new in Britain. Illicit drugs are sometimes laced with the class A stimulant, or a related substance called PMA (paramethoxyamphetamine). Five years ago, neither were known as killers in the UK. Since then, the rise in deaths has been worrisome. In 2012, 20 fatalities were recorded as PMA or PMMA-related. In 2013, the number rose to 29. Until now though, pills that contained such a strong dose were unknown.

The main effect of MDMA is to boost serotonin and dopamine levels, the feel-good chemicals in the brain. In contrast, PMMA blocks an enzyme that normally breaks down serotonin. The difference matters. The brain on PMMA cannot get rid of serotonin as fast as it should. Take enough and the drug induces serotonin syndrome, an overdose of serotonin that can lead to overheating, brain and vascular damage, and death.

Because PMMA can take two hours to have an effect, people take more. “They think they’ve had a dud pill so they take another one. And that puts them into a massive overdose,” Nutt said.

The Dutch alert was very specific. Similar-looking ecstasy pills were already on the market; they were also pink but the superman logo was only on one side. The other side had a groove to make the pills easier to break in half.

The lethal PMMA pills were probably made in the Netherlands and brought to Britain by ferry, where they stayed, in large part, in the south of the country. The Netherlands is the world’s biggest producer of ecstasy. PMA and PMMA are made when the same manufacturing process is fed different precursor chemicals. Because it is restricted, underground chemists have a tough time getting hold of a precursor for MDMA. But there is no legal barrier to importing the precursor for PMMA. It is also much cheaper.

According to Van der Gouwe, producers often cut drugs with small quantities of PMMA to make more money. But he is at a loss to explain why rogue chemists would make PMMA pills that are lethal. “It doesn’t make sense. We have no clue why it’s done,” he said.

Since the alert, the pills appear to have vanished from the Dutch market without anyone being harmed. “We believe our actions got rid of the tablets,” Van der Gouwe said.

The Dutch system appears to have worked well, and the UK has a similar, though fledgling, system called Wedinos that operates from Wales. But Measham argues that Britain needs a more agile system for monitoring dangerous drugs and wants to see more testing in clubs, festivals and other venues.

Ideally, people would talk to a specialist in drug harm reduction before having their drugs analysed. With her equipment, tests are completed in 60 seconds, compared with several days for the Welsh and Dutch systems, meaning people must plan their drug-taking in advance.